The invention relates to a yarn travel monitoring device containing a piezoelectric transducer for producing a signal depending on the tensile force of a textile thread.
Apart from the known transducers working with strain gauges or capacitively, and delivering a signal depending on the tensile force of the thread, piezoresistive transducers are also known which, although they are distinguished by a high sensitivity and accuracy, nevertheless are only suitable for use in laboratory research installations and not for installation in or on machines processing threads. This is because the inevitable vibrations and natural oscillation of such machines are also detected by the piezoelectric element of the transducer and are thus superimposed as spurious signals on the signal depending on the tensile force of the thread.
In itself, a piezoelectric transducer would, because among other things of its low sensitivity to dirt and its mechanical robustness, be eminently suitable to be installed in or on machines processing threads, but hitherto the above-mentioned disadvantageous properties stood in the way of this kind of use.